I would swap the whole rear end and hydro unit assembly and if you are worried about the relief valves, take the ones out of the 149 hydro unit and put them in the 1250 unit. That way you will know you have good relief valves.
Jason - swap the rearend but reuse your hydro pump and all the linkage set up on the 149. While you're at it you'll need to replace the "infamous cork gasket" where the pump mounts to the rearend. Only issue is whether the 1250 has internal wet brake or external disc like the 149 - hopefully the latter so you won't have more work.
Charlie - ok, Jason's a bit new on the bent axles, so I'm gonna call your bluff - show us your hand. Have you got 6 pairs of bent axles? No fair using a Royal Hydro Flush either.
Well Jason, at least you'll have plenty of spare parts. Maybe you can trade for other items you need for the 149. I would choose a 149 over 1250 anyday. My luck seems to be with quietlines. Although, I cannot wait until the 782 is up! Dad had driven it a bit and has laid claim to it for mowing out at a friends place this summer. He asked about power steering... One tractor at a time! Lol. 1450 is still going good mowing at his church, he likes that way more than the 1200, not a gear drive man anymore, or strong arm for that matter. Hydro lift has spoiled him.